RU2037845C1 - Airborne radar - Google Patents

Abstract

FIELD: radiolocation and radio navigation. SUBSTANCE: device has coherent transmitter 1, transmitting antenna 2, M-element receiving array 3, diagram forming unit 4, N units 5 of forming difference signals, 2N-channel receivers 6, N units 7 of angular velocity selection, two analog-to-digital converters 9 and 11, ground speed computing unit 10 and synchronization unit 12. This makes it possible to measure ground speed by phase method. EFFECT: enhanced efficiency. 5 dwg

Description

 The invention relates to radar and radio navigation and can be used in airborne avionics systems, in particular in airborne surveillance radars.

 Known aircraft detector of moving targets with a multipath antenna. In the transmitting part of the detector, a multi-beam pattern is formed. A digital processing system that implements Doppler filtering allows you to process the signals of many targets in large volumes of space in which the survey is carried out. The device contains a coherent transmitter (PRD), a Butler matrix for forming a beam, a transceiver antenna array (AR). Using the formation of zeros of the receiving diagram, suppression of interfering reflections received along the side lobes is suppressed.

 The disadvantage of this and other survey radars is that, while receiving and processing signals reflected from the earth’s surface, they do not measure ground speed and special devices are used for measuring ground speed.

 Known Doppler ground speed meters based on measuring the average frequency of the Doppler spectrum of a signal reflected by the earth's surface.

 The disadvantage of such devices is the low accuracy of measuring ground speed, due to the inability to form a narrow main lobe of the receive antenna radiation pattern and due to the influence of interference received by the side lobes.

 Known devices for measuring ground speed, based on the correlation principle, including a driver of the initial probing signal, primary measuring transducers that generate signals that depend on the interaction of the object with the mutual velocity medium, and correspond to the reception of reflected signals by different beams of the receiving antenna, and a transport delay correlation meter ( KITZ), ground speed calculation unit. At the same time, KITZ includes a correlometer and an extreme regulator. In the correlation meter, the input signals are similar in shape to each other, but have transport delays with respect to each other. The desired velocity value is a determinate function of the transport delays, and the transport delays themselves are determined by searching for the maximum of the mutual correlation function of the input signals. This procedure is performed by the KITZ unit.

 The disadvantage of these devices is also the low accuracy of measuring ground speed. Known devices for measuring ground speed are complex stand-alone devices, besides they give low accuracy in measuring ground speed, so it is advisable to measure ground speed using survey radar equipment with effective suppression of interfering reflections.

 The closest in technical essence is a radar containing a coherent PRD, the output of which is connected to the input of the transmitting antenna, the M-element receiving AR, the M-outputs of which are connected to the M-inputs of the beam-forming circuit (DOS), the N-outputs of which are connected to the N-inputs N-channel receiving device (PFP), the N-outputs of which are connected to the N-inputs of the N-channel analog-to-digital converter (ADC), the N-outputs of which are connected to the N-inputs of the unit for calculating the ground speed, synchronization device (US), the first whose output is connected with the input of the PRD, and the second output with the input of the N-channel PRM.

 The disadvantage of this device is that it does not allow to measure ground speed.

 The purpose of the proposed device is to expand the functionality of the onboard surveillance radar, namely the measurement of the ground speed of the radar carrier.

 This is achieved by the fact that N blocks of the formation of differential signals (FRS), a second N-channel PFP, a second N-channel ADC, N blocks of angular velocity selection (CSS) are introduced into the known device.

 The essence of the invention is to determine the directional speed of the radar carrier by the phase method, while receiving information about the phase change of the signal reflected from the earth's surface with the CSS unit of the on-board radar.

 The known principle of measuring speed by changing the phase of the reflected signal for a known time interval. In addition, it is known that the underlying surface can be considered as a set of mirror points and the reflection from them can be considered as reflection from a stationary object. For a small repetition period of the emitted signals, at real speeds of the aircraft (LA) and at a radiation wavelength of a few meters (for example), the movement of the aircraft relative to the reflecting surface can be less than the wavelength and the phase difference of the reflected signals can be measured unambiguously. This allows you to measure the speed of the aircraft phase method. At the same time, USS blocks are used to measure the phase difference, which in turn use the output signals from the Fed and DOS blocks.

 It is known that the formation of total and difference radiation patterns and the use of CSS for processing received signals makes it possible to narrow the main lobe, suppress the interfering reflections received by the side lobes, and, therefore, measure the phase of the received signals more accurately. The formation of the sum and difference signals can be carried out by adding and subtracting the signals corresponding to individual rays of the beam. CSS blocks generate signals corresponding to the phase change of the reflected signals during the repetition period, which are used to calculate the speed of the aircraft in the computing device.

 In FIG. 1 shows a block diagram of an airborne radar; figure 2 is a block diagram of the Fed block; in FIG. 3 block diagram of the CSS unit; figure 4 obtained on a mathematical model, the dependence of the error of measuring the speed of the carrier of the radar from its speed; in Fig. 5, the dependence of the velocity measurement error obtained on the model depending on the ratio of the interference power to the noise power (at a ground speed of 140 m / s).

 The proposed device (Fig. 1) contains a coherent transmitter 1, a transmitting antenna 2 (which may be an AR), an M-element receiving antenna array 3, a beam-forming block 4, N blocks of differential signal generation 5, a first N-channel receiver 6, N blocks USS 7, a second N-channel receiver 8, a first N-channel ADC 9, a ground speed calculating unit 10, a second N-channel ADC 11, a synchronization unit 12.

 The fed block 5 (Fig. 2) consists of M / 2 phase inverters (FI) 12, the M / 2 inputs of which are the first M / 2 inputs of the fed block 5 and are connected to the corresponding N / 2 outputs of DOS 4, while M / 2 outputs FI 13 are connected to the first M / 2 inputs of the SUM 14, the second M / 2 inputs of which are the corresponding second M / 2 outputs of the DOS 4, which are simultaneously the second M / 2 inputs of the FRS block 5, and the output of the SUM 14 is the output Fed block 5.

 The CSS unit 7 (Fig. 3) consists of a first delay line (LZ) 15, the input of which is the second input of the CSS unit 7 and connected to the first input of the SMS 16, the first correlator (K) 17, the first input of which is connected to the output of the first LZ 15 and the first input of the first multiplier (U) 18, the output of which is connected to the second input of the SMS 16, the third input of which is connected to the output of the second U 19, the first input of which is the first input of the CSS unit 7 and connected to the first input of the second KOR 20, the output of which is connected with the second input of the second Y 19. In this case, the second input of the second KOR 20 is in the second output of the CSS unit 7 and is connected to the second input of the first correlator 17 and the first input of the third KOR 21, the output of which is connected to the first input of the third Y 22, the second input of which is connected to the second input of the third K 21 and the output of the second LZ 23, the input of which is connected to the first input of the CSS unit 7. In this case, the output of the third U 22 is connected to the fourth input of the SMS 16, and the output of the first K 17 is connected to the second input of the first U 18 and is the first output of the CSS unit 7.

The proposed device operates as follows. The coherent transmitter 1 generates pulsed signals with a repetition period T _p , which are transmitted using the transmitting antenna 2 towards the underlying surface, the reflected signals are fed to the M-element receiving AR 3, from the outputs of which the signals are sent to block 4, which can be made in the form Butler matrix and with the help of which signals are generated, corrected in phase and corresponding to N radiation beams (total signals).

 The signals from the intermediate outputs of block 4 (from the outputs to the adders) arrive at blocks 5, in which differential signals are generated, which, along with the total output signals of block 4, are amplified, filtered, and gated in the second receiver and the first receiver and fed to the corresponding inputs of the CSS units 7 in which suppression of spurious signals received along the side lobes, narrowing of the main lobe and measuring the phase difference of the signals reflected from the underlying surface and spaced from each other by time and interval equal to T.

, где N количество лучей ДН приемной АР;
λ длина волны;
Т_п период повторения зондирующих импульсных сигналов;
φ_i разность фаз, измеряемая в i-м блоке углоскоростной селекции;
γ_i угол между вектором скорости и направлением максимума i-го парциального луча диаграммы направленности приемной антенной решетки.LZ 15 provides a time delay equal to T, the second LZ 23 2T _p . The signals corresponding to the phase differences are digitized by the ADC 9 and enter block 10, where the ground speed of the aircraft is calculated in accordance with the formula
v

where N is the number of beams of the receiving antenna AR;
λ wavelength;
T _p the repetition period of the probe pulse signals;
φ _i phase difference, measured in the i-th block of angular velocity selection;
γ _{i is the} angle between the velocity vector and the direction of the maximum of the i-th partial beam of the radiation pattern of the receiving antenna array.

 From the second outputs of the CSS units 7, signals with suppressed interference components are digitized in the ADC 11, fed to the WU 10 and used to detect targets and track their trajectories. CSS 12 synchronizes the Tx 1 and the second PfP 6 and the first PfP 8.

 On a PC, radar modeling was performed and calculations were performed to evaluate the accuracy of ground speed measurements. The calculation results for the case of radar operation in the meter wavelength range are shown in FIGS. 4 and 5. Correlation (most accurate) ground speed meters operating in the optical wavelength range provide a measurement accuracy of 01, -0.3% and in the radio range of unity and tens of percent. Thus, measurements of ground speed in the radio range using the proposed device are carried out with greater accuracy, which is an additional advantage.

Claims (1)

Aircraft radar station, containing a coherent transmitter, the output of which is connected to the input of the transmitting antenna, an M-element receiving antenna array, M outputs of which are connected to M inputs of a beam-forming unit, a first N-channel receiver, a first N-channel analog-to-digital converter, a calculation unit ground speed, synchronization unit, characterized in that N differential signal generating units, a second N-channel receiver, N angular velocity selection units, a second N-channel analog-digital are introduced into it ohm converter, while the first N · M outputs of the beam-forming block are connected to N · M by the corresponding inputs of N differential signal generating blocks, the outputs of which are connected to N inputs of the second N-channel receiver, N outputs of which are connected to the first inputs of N angular selection blocks, the first N outputs of which are connected to N inputs of the first N-channel analog-to-digital converter, N outputs of which are connected to the first N inputs of the unit for calculating ground speed, while the second N outputs of the beamforming the eyes are connected to the N inputs of the first N channel receiver, the N outputs of which are connected to the second inputs of the angle-speed selection blocks, the second outputs of which are connected to the inputs of the second N channel analog-to-digital converter, the N outputs of which are connected to the second N inputs of the ground speed computing unit, the first output the synchronization unit is connected to the input of the transmitter, the second output to the (N + 1) -th inputs of the first and second N-channel receivers, while the value of V ground speed is calculated by the formula

where N is the number of beams of the radiation pattern of the M-element receiving antenna array;
λ wavelength;
T _p the repetition period of the probe pulses of the signals;
v _i phase difference, measured in the i-th block of angular velocity selection;
γ _{i is the} angle between the velocity vector and the direction of the maximum of the i-th partial beam of the radiation pattern of the M-element receiving antenna array.

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